## Explain the reasoning behind Eq. (7.20) for normal anisotropy, and Eq. (7.21) for planar

1.Explain the reasoning behind Eq. (7.20) for normal anisotropy, and Eq. (7.21) for planar

anisotropy, respectively. Equation (7.20) on p. 391 represents an average

R value by virtue of the fact that all directions (at 45circ intervals) are taken into account.

2. Describe why earing occurs. How would you avoid it? Would ears serve any useful purposes?

Explain. Earing, described in Section 7.6.1 on p. 394, is due to the planar anisotropy of the sheet metal. Consider a round blank and a round die cavity; if there is planar anisotropy, then the blank will have less resistance to deformation in some directions compared to others, and will thin more in directions of greater resistance, thus developing ears.

### Explain why of length-of-bend to sheet thickness increases.

As noted in Fig. 7.16, the state of stress shifts from plane stress to plane strain as the ratio   of length-of-bend to sheet thickness increases. Explain why. This situation….

### Describe the material properties that have an effect on the relative position of the curves shown in Fig. 7.19.

Describe the material properties that have an effect on the relative position of the curves   shown in Fig. 7.19. Observing curves (a) and (c) in Fig. 7.19 on p…..

### Why do tubes have a tendency to buckle when bent?

Why do tubes have a tendency to buckle when bent? Experiment with a straight soda straw, and describe your observations. Recall that, in bending of any section, one-half of the….